The world judged by the Mosaic law

Now we know that whatever the law says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God. (Romans 3:19)

There are two possible interpretations of how Paul comes to that verse as far as I can see (this may again be due to my lack of research).

1. Having established that Gentiles are condemned by natural law (as is clear by the blatant sinning of Gentiles displayed Romans 1) Paul then had to show that the religious Jews are also sinners. This he does in Romans 2-3:18. Therefore having dealt with both he can conclude that the whole world is sinful because everyone is either Gentile or Jew.
2. The law condemns Israel. Israel represents the world as a priestly and kingly nation. Therefore the rest of the world is condemned 'in Israel'.

I think 2. is the right interpretation. Therefore the whole world is judged by the same law but in an order - the Jew first, and then the Greek.

This post parallels my last in being a reflection of my continuing feeble attempts to understand Romans. I would love to hear criticism. I should also do more reading, but I am so constrained by time. Out of ignorance I make wild stabs hoping over time and continual reading something sticks.